Liquid crystal panels used in liquid crystal display devices such as, for example, liquid crystal TVs, do not emit light themselves and require a backlight unit as an additional lighting device. The backlight unit is installed on the backside (opposite to the display surface) of the liquid crystal panel, and includes a chassis with an opening in the surface on the liquid crystal panel side, light sources housed in the chassis, a reflection sheet arranged along the inner surface of the chassis for reflecting light toward the opening of the chassis, and an optical member (such as a diffuser sheet) disposed at the opening of the chassis for directing the light emitted from the light sources efficiently toward the liquid crystal panel.
Some backlight units having the configuration described above use LEDs as the light sources for reducing power consumption, in which case, for example, a multiplicity of LEDs may be arrayed in a planar arrangement on a bottom plate of the chassis. One problem with such backlight units was that dark areas were created in four corners of the screen when observed from the front due to a shortage of light emitted from the backlight unit. The following Patent Document 1 describes a technique proposed to solve this problem.
Patent Document 1: Japanese Unexamined Patent Publication No. 2006-120644